Chapter 94 It’s not a blessing to know

When Zhang Donglin saw the experimental data recorded by his junior brother, his first feeling was that he was a little confused.

But after all, he had been studying for a doctorate for three years, and he quickly found something valuable from the mess of numbers.

"interesting……"

Although as his junior brother said, the stability of these sets of experimental data he produced was very poor.

But if you ignore the huge variance and just take the average value, you can still find that when the Mach number Ma=0.40 and the angle of attack are 0°, 3° and 6° respectively, the corresponding total pressure loss coefficients are reduced by 7.0% and 32.1 respectively. % and 32.3%, the average airflow turning angle increased by 4.02°, 3.59° and 1.78°, and the stable working range increased by 3.5° angle of attack.

Obviously, this is quite an amazing improvement.

However, the calculation method of "ignoring the variance and taking the average directly" is obviously difficult to achieve, and Zhang Donglin has to make sure that the result can be reproduced and is not due to some kind of misoperation.

Looking at the experiment record book in front of him, he took two deep breaths in succession:

"Junior brother, I want to see the process of your experiment just now. Can you repeat it exactly?"

"Ah...of course, no problem."

In the next two hours, Zhang Donglin watched his junior brother perform repeated experiments with skillful movements while taking out a notebook to record some of his thoughts and ideas.

With such exaggerated fluctuations, the experimental results are naturally somewhat different from just now, but the overall pattern remains the same.

The chordal groove accidentally opened during manufacturing can indeed improve the performance of the compressor to a considerable extent, especially the performance under large intake angles of attack.

Judging from the few sets of data currently available, the faster the air intake speed and the larger the angle of attack of the compressor, the more obvious the improvement effect will be.

In addition, Zhang Donglin also wrote down several factors that may affect performance, such as the location (height) of the slit, the shape and angle of the slit, etc.

But before he finished writing the last part, he knew that it would be difficult for his small research group to fully understand this issue.

Compared with the leaf tip consistency and accumulation line that they are currently focusing on, there are actually so many independent variables related to this slit that it feels a bit outrageous.

More importantly, the compressor experimental equipment at Bingcheng University of Technology can only support typical subsonic research at the maximum Mach number Ma=0.59.

With some tangled feelings, Zhang Donglin found his mentor Yu Fei.

"This...how is this possible?"

After seeing the data in the experimental notebook and listening to Zhang Donglin's analysis, Yu Fei's first reaction was almost exactly the same as that of his students:

"This kind of chordwise slit will cause the small flow turbulence with low total pressure and the mainstream with high total pressure to meet. The velocities are added on the vector. The velocity of the mainstream fluid decreases and the velocity of the wake fluid increases. This process will produce serious consequences. How could the mixing loss and total pressure loss coefficient be reduced instead?”

"In addition, the volatility of this original data is too great. I estimate that the correlation coefficient may not even be 0.7. How dare you directly average this kind of data?"

"But I asked my junior brother to repeat this experiment again, and the results still showed the same pattern." Zhang Donglin did not intend to give up this opportunity:

“And you also have to consider that although blade slits will increase mixing losses, they can also play a blowing role and delay the large-scale boundary layer separation of the blade cascade. There should be competition between these two effects. The relationship is right!”

"..."

The master and apprentice looked at each other in silence for a few seconds.

As mature scientific researchers, they know that it is impossible to solve the problem by bickering here.

Yu Fei supported his chin with one hand and beat the beat on the table with the other hand almost unconsciously. After thinking for a few minutes, he spoke again:

"You know, the flow loss inside the compressor is still almost a mystery to us at present. If we want to study this problem from a mechanism perspective... I am afraid it will be difficult to get the answer."

"But if you do an experiment..."

He didn't say it directly, but even Zhang Donglin knew that the laboratory at Bingcheng University of Technology did not have this capability.

The office fell silent again.

"In this way, you first design a set of experiments and do everything that can be done in our laboratory. Considering that the research in this area is still basically blank, I think if we put more effort into it, we can publish an article Journal of Aeronautics or Journal of Aerodynamics shouldn’t be a problem.”

"But... the effect of such research should be discounted, and we simply can't do the supersonic or even high subsonic compressor part. I think..."

"I know what you mean,"

Before Zhang Donglin could finish his words, he was interrupted by Yu Fei raising his hand:

"How to deal with the following matters depends on the results you make next. If it cannot be determined below the classic subsonic speed, then this direction is basically equivalent to being blocked. It is safer to return to the original position as soon as possible. on the route.”

"And if the experimental results show that your two ideas are correct...then this will be a major breakthrough in the field of compressor design."

After hearing the last few words, Zhang Donglin's eyes lit up:

"A big breakthrough?"

As a doctoral student at Bingcheng University of Technology, he knows the weight of these four words very well.

"But...don't be too happy too early."

Yu Fei looked at Zhang Donglin who looked like a fox with his tail raised and said:

"As you just said, our hardware here is limited and we can't do more in-depth research, so I'm going to report it to the Commission of Science, Technology and Industry for National Defense and let them organize manpower to conduct a comprehensive evaluation."

"That's why I just asked you to take advantage of this time to quickly conduct experiments and formulate an article to send out. On the one hand, it is possible for you to directly participate in the projects of the National Defense Science and Technology Commission, and on the other hand, you can at least leave something for yourself. .”

"Besides, aren't you just one thesis away from graduation requirements?"

This last sentence convinced Zhang Donglin, and he decided to solve the immediate graduation problem first, and then consider how much more he could dig out from his unintentional discovery.

So, after two months of experiments, submissions and waiting, a paper titled "Numerical Analysis of Blade Cascade Characteristics after Slotting from Pressure Surface to Suction Surface" appeared in the Journal of Aerodynamics.

At almost the same time, Yu Fei reported this paper as a key achievement to Bingcheng University of Technology's direct superior, the Commission of Science, Technology and Industry for National Defense, saying that this achievement had the potential for further follow-up research.

Needless to say, the efficiency of Zhang Donglin and Yu Fei is still a bit slow.

If we follow the normal administrative procedures, this topic will still come to the 606 Institute, but there is a high probability that it will not be able to keep up with the technological improvements of the Turbojet 14.

Fortunately, one day after work, Yao Mengna went to the library to borrow a book to read. She noticed this paper and borrowed it out of curiosity and took it back to the computer room.